1. Field of the Invention
This invention relates to a torque sensor suitable for use in a steering device of a vehicle, etc.
2. Discussion of the Prior Art
A valve operating mechanism for a conventional power steering device control valve is disclosed, for example, in U.S. Pat. No. 2,964,017 to Howard E. Hruska. This conventional device is not a torque sensor but has a specific structure in which, as shown in FIG. 1, a slide cylinder 3 on a main shaft 1 is coupled by springs 5 to a fixed sleeve 4 on a follower shaft 2. The rotation of the main shaft 1 causes the slide cylinder 3 to move axially to transmit an axial shift of the slide cylinder 3 to a spool (not shown).
According to such conventional valve operating mechanism, the respective springs 5 at an attitude inclined at 45 degrees at the neutral steering position change their attitude such that the respective springs gradually increase or otherwise decrease their inclination as the main shaft 1 rotates. Therefore, the quantity of axial shift of the slide cylinder 3 for unit angular rotation of the main shaft 1 varies depending upon the angle phase thereof. As a result, an imbalance occurs in the quantities of shift of the spool valve occurring when the steering wheel is rotated clockwise and counterclockwise, respectively. Therefore, if such an operating mechanism is applied to the torque sensor, the sensed torque value would vary depending on the direction of rotation of the main shaft even if the same torque may act on the main shaft.